1. Field of Invention
The present invention relates generally to automobile wheel alignments, and more specifically, to an improved, portable wheel alignment device and system.
2. Description of Related Art
A wheel alignment, also known simply as an alignment, is a measurement and adjustment of angles of a vehicle's wheel suspension to a desired and/or optimal performance configuration. Generally, a wheel alignment includes adjusting the angles of the wheels so that they are set within the car maker's specifications. Alignment angles can also be altered beyond the maker's specifications for sport and off road performance. Correct adjustment of the suspension angles is critical to balance the tire tread wear and to ensure that the vehicle travels straight. Regular wheel alignments are considered to be routine preventative maintenance.
Out-of-alignment conditions occur when the suspension and steering systems are not operating at their desired angles. The primary angles are the basic angle alignment of the wheels relative to each other and to the car body. These angles include the camber angle (i.e., vertical angle of wheel when viewed from front or rear), the caster angle (i.e., angle between the pivot line and vertical), and toe (i.e., symmetric angle that each wheel makes with the longitudinal axis of the vehicle). Secondary angles include numerous other adjustments, such as without limitation, steering axis inclination (SAI), included angle, bump steer, maximum turns, toe curve change, track width difference, wheel base difference, front ride height, rear ride height, and frame angle.
Out-of-alignment conditions are most often caused by spring sag or suspension wear on an older vehicle, but can also be caused from impact with a pothole, curb, rocks, or a change in vehicle ride height. This will usually result in more rapid tire wear and decreased fuel economy. The alignment should be checked whenever new tires or suspension components are installed, any time unusual tire wear patterns appear, after the vehicle has encountered a major road hazard, pothole, or curb, among other occasions (e.g., when the vehicle drifts, pulls, or otherwise handles unusually, when the vehicle vibrates, when the steering wheel is not centered, during periodic safety checks, for custom performance, and when there are worn components such as ball joints, arms, struts, shocks, or springs).
The optimum alignment of the vehicle depends on the driver's driving style. For a commuter driver, aligning the vehicle to the vehicle manufacturer's preferred settings is appropriate. Although there are acceptable angle ranges provided in the manufacturer's recommendations, the wheel alignment should align the vehicle to the preferred settings, and not just simply within the range. For an assertive or competitive driver, someone who enjoys driving hard through the corners, a performance alignment is appropriate. The performance alignment maximizes the performance of the tire. The performance alignment uses a maximum negative camber, maximum positive caster, and aggressive toe settings.
Three common types of wheel alignments offered are: a front-end wheel alignment, a thrust angle wheel alignment, and a four-wheel alignment. The front end wheel alignment only measures and adjusts the front axle's angles, and is sufficient for vehicles with a solid rear axle and where the front tires are positioned directly in front of the rear tires. The thrust angle wheel alignment is for the solid rear axle, which requires a technician to confirm that all four wheels are square with each other, to prevent the vehicle from going down the road with the rear end offset from the front end, otherwise known as a dog tracking. Four wheel alignments are needed for vehicles with four-wheel independent suspensions, or front-wheel drive vehicles with adjustable rear suspensions. This procedure squares the vehicle like a thrust angle alignment, and also includes measuring and adjusting the rear axle angles as well as the front.
An optical sensor unit (also known as a head, optical sensor, laser sensor, etc.) is often attached to a clamp which holds on to a wheel. There is usually one optical sensor per wheel in a wheel alignment system, meaning four optical sensor units for a car having four wheels. These optical sensor units communicate their physical positioning with respect to other optical sensor units to a central computer which calculates and displays how much the camber, toe and caster are misaligned. Conventional measurements are typically performed with the vehicle's wheel (i.e., tire) not removed from the vehicle.
When aligning a vehicle, it is appropriate for the vehicle to be carrying its typical load. This is important for drivers who continuously carry loads in their vehicles. Additionally, when a vehicle is used for autocross or track events, some racers will sit in their car, or have the alignment shop ballast their vehicle to include the influence of the driver's weight on the suspension angles.
Corner weighting (also known as corner balancing, weight jacking, and scaling) involves adjusting the spring perches of a car to get a balanced diagonal weight on the tires. Ideally, the car should have 50% of its weight on the left front and right rear tires and 50% on the right front and left rear tires. In other words, the suspension of the car has to be adjusted so that each corner of the car applies the same amount of force on the ground, relative to the diagonally-opposite corner of the car, so that the car does not rock back and forth. To measure corner weight, scales can be placed underneath each tire to measure the weight of each corner. An ideal corner balance would have the sum of the weights of the right-front and left-rear corners equal to the sum of the weights of the left-front and right-rear corners. If the car's corner weights are not equal, then the car's the tires may wear unevenly and the handling may be unbalanced, in that the car will turn better in one direction than in the other direction.
Conventional alignments are typically performed using an alignment rack. The vehicle is driven onto the alignment rack, which allows access to the underside of a vehicle while the chassis rests its full weight on all four wheels on a level surface in order to carry out alignment measurements and adjustments. The primary static suspension angles that need to be measured and adjusted are camber, caster, toe, and thrust angle. The alignment rack has movable slip plates that go under the vehicle's wheels that relieves the pressure off the suspension and allows the suspension to settle prior to the alignment.
Alignment racks are large, often approximately 20 feet long and 8 feet wide, which takes up valuable space such as a whole bay in a mechanic's shop, which prevents many small mechanical shops from doing alignments all together. In addition, these alignment racks are stationary and do not lend themselves to being portable and performing alignments outside of the garage. Further, alignment racks are expensive, often costing $50,000 to $100,000, which further prevents small mechanic shops from doing alignments. Moreover, alignments using alignment racks take approximately an hour, which makes them time consuming. Conventional alignment devices lack many useful features that prevent many mechanic shops from even doing alignments. Further, conventional alignment tools do not relieve the pressure off the suspension or allow the vehicle's suspension to settle prior to an alignment producing less accurate alignments.